The correct answer is C) cities.
In the Desert Valley, the poet says that the villagers will either go to America or to crowded, corrupted cities.
In the Desert Valley, the villagers are driven from their home because the enclosure acts have enabled a wealthy landowner to buy the public property. The people from the Valley were forced to leave their places and go to America. That is the reason why the valley became desert. The Poet also refers that the people of England were too corrupted by wealth.